This invention relates to method and apparatus for producing large diameter storage tanks from strip metal. The invention is particularly directed to the production of such storage tanks in simplified fashion utilizing a combination of plate bending and welding.
It is known to produce large diameter storage tanks from strip metal, in which the strip is fed to a support assembly arranged circularly on a base for supporting the strip vertically in a helical path. McDonald U.S. Pat. No. 3,380,147 issued Apr. 30, 1968 discloses such a technique in which the strip is bent and welded. The bending of the strip, as disclosed in that patent, is a crimping of the top edge of the strip to provide an offset section so that the lower edge of the helical turn thereabove will fit into that offset section as it is fed over the top of the incoming strip of sheet steel. Double welding, both on the inside and outside of the tank, is required to secure adjacent helical turns of strip together.
It has also been proposed by others to bend both the top and bottom edges of strip steel in building a storage tank so that the adjacent edges of helical turns may be interfitted together and thereafter welded, as desired. While this construction produces a desirable outwardly extending helical fin on the storage tank, it does require the bending of both upper and lower edges of the strip steel and their interfitting together.
In the present application, only the upper edge of the strip is bent to substantially a right-angled bend, the bent upper edge is aligned with the unbent lower edge of the helical turn immediately thereabove, and the two aligned edges are welded together to produce a large diameter storage tank with a helical fin thereon constituted by the single right-angled bend in the strip.
The invention will be more completely understood by reference to the following detailed description, taken in conjunction with the appended drawing.